Tangible objects on interactive tabletop systems are a known means to provide input to such systems. For example, on the Reactable (http://mtg.upf.edu/reactable/) from the Music Technology Group, Pompeu Fabra University, Barcelona, the size of various tangible objects is used to identify different sound generators/modifiers, and the orientation of these is used to control an input parameter (e.g., amount of contribution to the end result). Tracking is done via computer vision from beneath the table. For the Reactable, only the identity, position and orientation of the objects are input parameters, that can be manipulated for the purpose of user interaction with the system.
The SenseTable from MIT is an example where the objects, that form an input method on an interactive surface, also have a second input method on the objects themselves. The objects of the SenseTable have a dial controller on top, of which its state, plus the position of the object is tracked electromechanically. Also other input means are known, such as those described in WO2006/082547-A2: tangible objects with triggerable subparts (e.g., touch sensitive areas). Communication of these objects to an interactive tabletop is described to be done via electrode contacts, charge (capacitive touch screen), wireless RF, or IR Light.
Such known tangible objects are quite suitable for providing interaction of the tangible objects with the interactive system. The objects themselves as well as their position and their orientation can be used as input for the interactive system. The dial controller or triggerable subpart may provide additional functionality related to the object. However, such tangible objects are not very useful for providing the functionality of a general pointing device. Pointing devices, such as joysticks, mice and track balls are well known. Alternative pointing devices such as touch pads, graphics tablets or light pens are also known. Such pointing devices allow a user to input spatial (i.e. continuous and multi-dimensional) data to a computer. Pointing devices may, e.g., be used for moving a cursor through a graphical user interface (GUI). Such pointing devices may also be used in combination with interactive surfaces, e.g., by plugging the pointing devices into a computer that is used for operating the interactive display. Such pointing devices may be wired or wireless, but will always require some additional energy source to allow communication with the system.
WO 2006/103676 A2 describes a way to use tangible objects on an interactive surface to provide some functionality of a pointing device. In WO 2006/103676 A2, a very large interactive surface is provided. A user or object on the interactive surface may function as a pointing device. Two techniques are disclosed. First, the display rectangular may be mapped onto a corresponding area on the interactive surface. The position of the user on the mapped area then corresponds to a position on the display. This is very similar to the use of a graphics tablet. Second, the position of the user relative to a Point of Equilibrium may be used to indicate a direction. This technique is very similar to the use of a joystick. If the top of a joystick is moved to the left of its centre position, a cursor will move to the left. The cursor stops moving when the joystick top is back at its centre position. Because WO2006/103676 A2 only uses manipulation of the position of the user or object on the interactive surface to provide special data, the system disclosed therein is not very suitable for, e.g., playing games requiring fast and accurate manipulation of the pointing device.
It is an object of the invention to provide a pointing device for use on an interactive surface, which pointing device allows fast and accurate manipulation without requiring an additional energy source for communicating with the system.